H3‐Receptors Control Histamine Release in Human Brain

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Abstract
The regulation of histamine release was studied on slices prepared from pieces of human cerebral cortex removed during neurosurgery and labeled with l‐[3H]‐histidine. Depolarization by increased extracellular K+ concentration induced [3H]histamine release, although to a lesser extent than from rat brain slices. Exogenous histamine reduced by up to 60% the K+‐evoked release, with an EC50 of 3.5 ± 0.5 × 10−‐8M. The H3‐receptor antagonists impromidine and thioperamide reversed the histamine effect in an apparently competitive manner and enhanced the K+‐evoked release, indicating a participation of endogenous histamine in the release control process. The potencies of histamine and the H3‐receptor antagonists were similar to those of these agents at presynaptic H3‐autoreceptors controlling [3H]histamine release from rat brain slices. It is concluded that H3‐receptors control histamine release in the human brain.